What's *your* latest mess-up?

[Th3_uN1Qu3]

There was no thread on this subject so why the heck not make one. Inspired by smason's story here, where he was ready to take the soldering iron to a power supply board when actually the switch was off, and having been thru such situations many time myself, such a thread will certainly be fun.

I'll start with my latest. I made a PCB for a class D amplifier. It didn't work, got really hot, and looked real bad on the scope. I thought my layout was bad so i made another PCB, this time double sided with ground plane. Same thing. Spent 2 days troubleshooting the new board. It no workie. Left it alone for another couple days then went back at it today. Discovered a number of inconsistencies compared to my ugly stripboard which did work, noticed i forgot to install some caps, but eventually it traced down to....

I had installed two diodes the other way round. That's right, got them wrong on the first board, got them wrong on the second board, and took me a week to realize it.